1. Field
Exemplary embodiments of the present invention relate to semiconductor device fabrication technology and, more particularly, to an image sensor including a phase-difference detection pixel.
2. Description of the Related Art
Most imaging devices, such as digital cameras and camcorders, adopt auto-focus systems. Auto-focus systems are divided into those that use a phase difference detecting scheme and those that use a contrast detecting scheme.
Phase difference auto-focus systems have a sensor for detecting phase differences in addition to an image sensor. Auto-focusing is accomplished by adjusting the lens based on an output of the phase difference detecting sensor. The phase difference detecting scheme also requires a mirror. For example, in an auto-focusing scheme for a Digital Single Lens Reflection (DSLR) camera, a sub-mirror for guiding incident light into a phase difference detecting sensor is provided in addition to a main mirror. The phase difference-based auto-focusing is advantageous in that it makes fast and high-performance auto-focusing possible. However, the phase difference-based auto-focusing is a high-cost system since it requires a sensor dedicated to the phase difference-based auto-focusing and an optical system.
In comparison, contrast detecting auto-focus systems rely on high-frequency data. This method of auto-focusing is referred to as contrast auto-focusing. Since contrast auto-focusing does not require a signal processing circuit or a phase detecting sensor, which are essential in the phase difference-based auto-focusing, contrast auto-focusing has a relatively low cost. However, contrast auto-focusing is slower and less accurate than phase difference-based auto-focusing.